GPZ 500 Idle problems

[gottogetbig]

Hi, I need some help.

My GPZ 500 starts up fairly good and easy. But it idles less than a 1000 and sounds like its struggling. With choke it idles about 1500. But I dont use it too often as I dont need to.

When I leave it ticking over it climbs fairly high. Went down to my mates about 10 minutes away and by the time I got off it was nearly on 3000 when it was idling.

Any ideas what it could be? I think because of the low tick over I turned it too high hence the 3000, but it takes time to climb that high so if I bring it down it will be really low when I first start it... it may not be that though as its always different, either way it isn't right and I am sick of adjusting it to get it to 1200 everytime I start it.

[pepperami]

So by reading your post I can establish that you are/have been fiddling around with the idle/tick-over screw on the carbs?

So what made you first decide to tweak them?, was it that your bike was starting to tick-over very slowly and almost stall?
If that was the case and it was my bike, I would be thinking along the lines of a blocked pilot jet maybe?

Or the floats in one of the carbs is not working? possibly, maybe?.

Or was it that the revs began to rise once the bike was warm?
that may indicate an air leak somewhere possibly, maybe, I think?

just a couple of thoughts
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I am the sum total of my own existence, what went before makes me who I am now!

[Glenben92]

Yeah I'd take the carbs off and give them a complete strip, clean and rebuild. Check the rubbers either side of both carbs for cracks or splits. Make sure there's a cap on the inlet manifold that isn't attatched to the tank's vacuum hose as well. (usually the right one)

I recently had an overfuelling problem in the right cylinder and it was the pin that holds the carb float arm to it's bracket; they're not held in by anything, it had slid out of one of its holes so it wasn't rising properly.

That's not your problem, but it's worth a mention for anyones future reference.
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57 Huoniao HN125-8 - , 97 Kawasaki GPZ500S -
99 Yamaha FZS 600 -
Mod 2 Passed - 01/10/2010

[stinkwheel]

Before you go pulling your bike to bits. Sounds to me like you have your starting drill arse-backwards and have set the idle speed way too high.

You should need the choke to start up a cold engine. This is the normal starting procedure. If you weren't meant to use the choke, they wouldn't have fitted one.

A cold engine idles slower, it is perfectly normal for a motorbike with a manual choke to stall-out on a cold engine if you don't use the choke. I have 5 bikes and I wouldn't expect any of them to idle properly on a cold engine without the choke. One of them has a GPZ500 engine in it.

Set your idle speed to a steady tickover with a warm engine. Start the on full choke from a cold engine. Then either back it off gradually as it warms up and the idle speed increases or ride away and knock the choke off on the fly then take it easy for the first couple of miles.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Suntan Sid]

This is exactly the problem my mate had on his ER5, wouldn't idle at low revs, once the idle speed was adjusted, afters 30 secs or so the idle speed would increase to around 3000rpm, no amount of adjustment to the carbs and idle srew made any difference.

Turns out there was a, tiny pin hole, air leak in one of the diaphragms.
A new diaphragm improved the situation by 90%.
A complete and very thorough, clean, strip down and rebuild of the carbs, with all new parts, cured the problem 100%!
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"Everybody needs money, that's why they call it money!"

[Dr. Quack]

Yeah give the carbs a good clean, needle and both pilots.
Also valves clearences, so I would give it a good service.

[gottogetbig]

I thought you only used the choke when it wouldn't start with out choke From now on I will use it everytime and let it warm up plenty

I started it today with choke, it was at 2000 for a split second then went down below 1000 with choke on. I went out and checked on it and it was at 1500. I could hear it going up and down and when I was ready it was at 3K so i took the choke off and it went to 2k

I have a spare set of ER5 carbs lying around that are already clean and came from my ER5 that was running fine. Am I right in thinking they are OK to use as long as I swap all the jets inside to the GPZ ones?

[stinkwheel]

[gottogetbig]